Monday, December 13, 2010

SEVEN SEGMENT CIRCUIT

The IC 4511 is a BCD to 7-segment decoder driver. Its function is to convert the logic states at the outputs of a BCD, or binary coded decimal, counter like the 4510 into signals which will drive a 7-segment display. The display shows the decimal numbers 0-9 and is easily understood.

7-segment display

There are two important types of 7-segment LED display. In a common cathode display, the cathodes of all the LEDs are joined together and the individual segments are illuminated by HIGH voltages. In a common anode display, the anodes of all the LEDs are joined together and the individual segments are illuminated by connecting to a LOW voltage.

The 4511 is designed to drive a common cathode display and won't work with a common anode display. You need to check that you are using the right kind of display before you start building.

The 0.56 in. 7-segment display common cathode available from Rapid works well as part of a prototype board circuit.When the 4511 is set up correctly, the outputs follow this truth table:

In normal operation, the lamp test and ripple blanking inputs are connected HIGH, and the enable (store) input is connected LOW. The circuit diagram shows the 4511 and a 7-segment common cathode display connected to the outputs of a 4510 BCD counter:

SEVEN SEGMENT CIRCUIT

To build this circuit follow the prototype board layout from the 4510 Beastie Zone web page and then add the 4511 with connections to a third prototype board, as shown below: